The present invention relates to an electrophotographic toner for developing electrostatic images in electrophotography, electrostatic recording, electrostatic printing, and the like, and an image forming apparatus.
In electrophotography, in order to fix toner images onto sheets such as paper or the like, toners are thermally melted and fixed. So-called heat melt fixing is frequently employed. The heat melt fixing is mainly divided into two types, i.e. flash fixing in non-contact, and heated roll or heated belt fixing in contact. Of these, the heated roll and heated belt fixing subjects toners to melt while allowing toner images to come into contact with a heat transfer member. As a result, it is possible to expect to obtain high thermal efficiency. Thus said fixing is effective particularly for electrophotographic copiers, as well as printers, which output images at a high speed.
However, since in such heated roll and heated belt fixing, the heat transfer member is brought into direct contact with melted toner images, offset phenomenon tends to occur, in which a part of the toner image is adhered and transferred onto the heat transfer member, and retransferred to the subsequent fixing sheet to stain the resulting images. Further, when the heat transfer member comes into contact with a toner image, contact charging phenomenon occurs and a phenomenon occurs in which said heat transfer member is charged. Electrostatic charge accumulated in said heat transfer member, prior to contact with the forthcoming heat transfer member, electrostatically repels or attracts an unfixed toner image and thus turbulence of images or so-called image dust tends to be caused. This phenomenon occurs markedly in an image forming apparatus which fixes said images at a high speed.
In order to minimize said offset phenomenon, the supply of releasing oil to the fixing roll or the incorporation of offset preventing agents (occasionally referred to as releasing agents) have been carried out. However, the supply of said releasing oil causes a fixing device to be relatively complex, as well as increasing its dimensions. In addition, it is difficult to conduct a stable supply of said oil. Thus, it is impossible to achieve sufficient minimization of the offset. Further, the incorporation of said offset preventing agents into the toner is relatively effective for minimizing the offset. On the other hand, however, problems are accompanied in which charging toner is hindered. As a result, the image dust tends to be caused and it is not always possible to obtain high quality images.
In order to minimize the retardation for charging toners, charge control agents have been tried. However, since the chargeability of said charge control agents is great, it is difficult to achieve uniform dispersion in the toners. In addition, the dispersion of said releasing agents is degraded due to the strength of its chargeability, and it is impossible to sufficiently obtain the expected offset preventing effects.
It is an object of the present invention to obtain a high quality fixed image which exhibits sufficient fixed strength in the broad fixable temperature range, as well as forms no image dust.
The present invention and its embodiments will now be described.
1. An electrophotographic toner which comprises a resinous composition for toners having at least two peaks, one at a lower molecular weight of 3,000 to 50,000 and the other at a higher molecular weight of 100,000 to 5,000,000 of the copolymer which is comprised of, as the main component, vinyl based copolymers comprised of styrene based monomers as well as acrylic or methacrylic acid ester based monomers as the structural units along with a fatty acid ester represented by the general formulas (1-1) through (1-4), and a carboxylic acid represented by the general formula (2).
R1RCOOR2xe2x80x83xe2x80x83General Formula (1-1)
(one or both of R1 and R2 represent an aliphatic group having at least 14 carbon atoms and when either R1 or R2 represents an aliphatic group having at least 14 carbon atoms, the other group may represent an alkyl group having no more than 14 carbon atoms, a cycloalkyl group, an alkenyl group, or an aralkyl group.)
[R1COOxe2x80x94(CH2)n]axe2x80x94Cxe2x80x94[(CH2)mxe2x80x94OCOR2]bxe2x80x83xe2x80x83General Formula (1-2)
(a and b each represents an integer of 0 to 4; a+b is 4; R1 and R2 each represents an organic group having from 1 to 40 carbon atoms; the difference in the number of carbon atoms between R1 and R2 is to be at least 3; m and n each represents an integer of 0 to 25; and m and n are not 0 at the same time.
[R1COOxe2x80x94(CH2)n]axe2x80x94Cxe2x80x94[(CH2)mxe2x80x94OH]bxe2x80x83xe2x80x83General Formula (1-3)
(a represents an integer of 0 to 4; b represents an integer of 1 to 4; a +b is 4; R1 represents an organic group having from 1 to 40 carbon atoms; m and n each represents an integer of 0 to 25; and m and n are not 0 at the same time.)
[R1COOxe2x80x94(CH2)n]axe2x80x94C(R3)kxe2x80x94[(CH2)mxe2x80x94OCOR2]bxe2x80x83xe2x80x83General Formula (1-4)
(a and b each represents an integer of 0 to 3; a+b is 1 to 3; R1 and R2 each represents an organic group having from 1 to 40 carbon atoms; the difference in the number of carbon atoms between R1 and R2 is at least 3; R3 represents a hydrogen atom or an organic group having at least 1 carbon atom (however, when a+b is 2, either one of R3 represents an organic group having at least 1 carbon atom); k represents an integer of 1 to 3; m and n each represents an integer of 0 to 25; and m and n are not 0 at the same time.)
xe2x80x83R4xe2x80x94COOHxe2x80x83xe2x80x83General Formula (2)
(R4 represents a saturated or unsaturated aliphatic group having at least 13 carbon atoms.)
2. An electrophotographic toner comprising a compound represented by general formula (3), described below, along with a resinous composition for toners having at least two peaks, one at a lower molecular weight of 3,000 to 50,000 and the other at a higher molecular weight of 100,000 to 5,000,000 of the copolymer which is comprised of, as the main component, vinyl based copolymers comprised of styrene based monomers as well as acrylic or methacrylic acid ester based monomers as the structural units. 
(R4 through R7 each represents a hydrogen atom or a univalent substituent; a plurality of these may be substituted or may have a ring structure including a condensed ring. Further, R4 through R7 may be the same or different. M represents a trivalent metal, and X represents a univalent or divalent positive ion which neutralizes the electrical charge.)
3. The electrophotographic toner described in 2. above comprising a fatty acid ester represented by said general formula (1) as well as a carboxylic acid represented by said general formula (2).
4. The electrophotographic toner described in 1., 2., or 3. above comprising a crystalline compound having a low melting point.
5. The electrophotographic toner described in 1., 2., 3. or
4. above comprising a polyolefin component.
6. An electrophotographic toner comprising a resinous composition for toners, which is comprised of a matrix phase along with a domain phase which is dispersed in said matrix phase, a fatty acid ester represented by said general formula (1), and a carboxylic acid represented by said general formula (2).
7. An electrophotographic toner comprising a resinous composition for toners, which is comprised of a matrix phase along with a domain phase which is dispersed in said matrix phase as well as a compound represented by said general formula (3).
8. The electrophotographic toner described in 7. above comprising a fatty acid ester represented by said general formula (1) as well as a carboxylic acid represented by said general formula (2).
9. The electrophotographic toner described in 6., 7., or 8. above, comprising a crystalline compound having a low melting point.
10. The electrophotographic toner described in 6., 7., 8., or 9, above, comprising a polyolefin component.
11. An electrophotographic toner comprising a resinous composition for toners, which is comprised of a matrix phase along with a domain phase which is dispersed in said matrix phase, and in which a compatibilizer is contained in said domain phase and/or said matrix phase along with a fatty acid ester represented by said general formula (1), and a carboxylic acid represented by said general formula (2).
12. An electrophotographic toner comprising a resinous composition for toners, which is comprised of a matrix phase along with a domain phase which is dispersed in said matrix phase, and in which a compatibilizer is contained in said domain phase and/or said matrix phase, along with a fatty acid ester represented by said general formula (1).
13. The electrophotographic toner described in 12. above, comprising a fatty acid ester represented by said general formula (1) as well as a carboxylic acid represented by said general formula (2).
14. The electrophotographic toner described in 11., 12., or
13. above, comprising a crystalline compound having a low melting point.
15. The electrophotographic toner described in 11., 12., 13., or 15. above comprising a polyolefin component.
16. The electrophotographic toner described in any one of 11. through 15. above, in which said compatibilizer is a compound comprised of a block copolymer or graft copolymer comprising the same component as the matrix phase as well as the domain phase.
17. The electrophotographic toner described in any one of 11. through 16. above, in which said compatibilizer is a compound comprised of a polymer having a group which is capable of forming either a hydrogen bond or an ionic bond.
18. The electrophotographic toner described in any one of 11. through 17. above, in which volume standard 10 percent average particle diameter D10, volume standard 50 percent average particle diameter D50, and volume standard 90 percent average particle diameter D90 satisfy the formula described below.
D10 greater than 0.5xc3x97D50
D90 less than 1.5xc3x97D50
19. An image forming apparatus wherein the electrophotographic toner described in any one of 1. through
18. above is employed, and said toner is melted by passing it through a heated roll and an image is formed by subjecting the resulting toner to be fixed onto an image carrying member.
20. The image forming apparatus described in 19. above, having therein a fixed heat generating member and a heated roll fixing device, employing a rotatable cylindrical heat transmitting member around said heat generating member.
21. The image forming apparatus described in 19. above, employing therein a rotatable cylindrical member and a heat generating member installed adjacent to the surface of said cylindrical member are employed.
22. An image forming apparatus wherein an image is formed in such a manner that while employing the electrophotographic toner described in any of 1. through 18. above, said toner is melted and fixed onto an image carrying member, employing a fixed heat generating member and a heated belt fixing device having endless belt-shaped heat transmitting member mounted around said heat generating member.
23. An image forming apparatus wherein an image is formed in such a manner that the electrophotographic toner described in any of 1. through 18. above, is employed, and said toner is melted by passing it through a flash fixing device and is subsequently fixed onto an image carrying member. 24. An image forming method wherein an image is formed employing an image forming apparatus described in any of 19. through 23. above.
The resinous composition for toners of the present invention includes a resinous composition which has a molecular weight distribution having two peaks, one in the high molecular weight region and the other in the low molecular weight region. Said resinous composition is obtained by blending, in addition to said resinous composition having a molecular weight distribution with two peaks, at least one type of ester represented by the aforementioned general formulas (1-1) through (1-4), a carboxylic acid represented by general formula (2), and a compound represented by general formula (3). By employing said resinous composition, the aforementioned offset is markedly minimized and sufficient chargeability, as well as fixability, is obtained.
The resinous composition for toners of the present invention is comprised of, as the main component, vinyl based copolymers composed of styrene based monomers and acrylic or methacrylic acid ester based monomers as the structural units.
The aforementioned styrene monomers include, for example, styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, xcex1-methylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-n-butylstyrene, p-tert-butylstyrene, p-n-hexylstyrene, p-n-octylstyrne, p-n-dodecylstyrene, p-methoxystyrene, p-phenylstyrene, p-chlorostyrene, 3,4-dichlorostyrene, and the like.
The aforementioned acrylic or methacrylic acid ester based monomers include, for example, acrylic or methacrylic alkyl esters such as methyl acrylate or methacrylate, ethyl acrylate or methacrylate, propyl acrylate or methacrylate, n-butyl acrylate or methacrylate, isobutyl acrylate or methacrylate, n-octyl acrylate or methacrylate, dodecyl acrylate or methacrylate, 2-ethylhexyl acrylate, stearyl acrylate, and the like, further 2-chloroethyl acrylate, phenyl acrylate or methacrylate, methyl xcex1-chloroacrylate, dimethyl aminoethyl methacrylate, diethyl aminoethyl methacrylate, 2-hydroxyethyl methacrylate, glycidyl methacrylate, bisglycidyl methacrylate, polyethylene glycol dimethacrylate, methacryloxyethyl phosphate, and the like. Of these, methyl methacrylate, ethyl acrylate or methacrylate, propyl acrylate or methacrylate, n-butyl acrylate or methacrylate is particularly preferred.
The aforementioned vinyl based copolymers may comprise other vinyl based monomers. Such other vinyl based monomers include, for example, acrylic or methacrylic acids and xcex1- or xcex2-alkyl derivatives thereof such as acrylic or methacrylic acid, xcex1-ethylacrylic acid, crotonic acid, and the like; unsaturated dicarboxylic acids and monoester or diester derivatives thereof such as fumaric acid, maleic acid, citraconic acid, itaconic acid, further monoacroyloxyethyl succinate, metacryloyloxyethyl succinate, acrylonitrile or metacrylonitrile, acrylamide, and the like.
In the present invention, employed are copolymer compositions for the toner, having a peak in each molecular weight distribution. Namely, these copolymers are comprised of one having a molecular weight distribution preferably in the range of 3,000 to 50,000 in terms of the weight average molecular weight, more preferably in the range of 5,000 to 20,000, and most preferably in the range of 8,000 to 15,000 in the low molecular weight region, and the other having a molecular weight distribution in the range of 100,000 to 5,000,000, preferably in the range of 500,000 to 2,000,000, and more preferably in the range of 800,000 to 1,200,000 in the high molecular weight region.
Said copolymer compositions having two peaks in their molecular weight distribution may be obtained, for example, by simply blending two binder resins, prepared separately, under the various conditions described below. However, it is preferable that low molecular weight polymers or high molecular weight polymers are previously produced and if desired, vinyl type monomers as well as polymerization initiators are further added in the presence of the compatibilizers described below, and for instance the resulting mixture may undergo radical polymerization in the solution. By such polymerization, a binder resin having the molecular weight distribution having peaks is obtained. In the aforementioned preferred examples, two molecular weight components constitute a uniform domain structure without causing pronounced layer separation.
Namely, the resinous composition for toners of the present invention is the one which is formed by matrix phases as well as domain phases dispersed in said matrix phases.
In said resinous components of the present invention, those composing the matrix phases are comprised of low molecular weight vinyl based resinous components. The weight average molecular weight of said components is between 3,000 and 50,000. The glass transition temperature of the same is preferably at least 50xc2x0 C., but is more preferably between 50 and 75xc2x0 C. The content of the same is preferably between 60 and 95 weight percent by weight with respect to the entire resinous components, and is more preferably between 65 to 90 percent by weight. Such low molecular weight vinyl based components are soft and tough, and markedly affect fixability at low temperature, as well as offset resistance. By controlling said resinous components to stay within the aforementioned ranges, the fixability as well as the offset resistance is further improved.
Further, the resinous components composing the domain phases are comprised of high molecular weight vinyl based components. The glass transition point Tg of said components is preferably between 50 and 75xc2x0 C. The weight average molecular weight of the same is preferably between 100,000 and 5,000,000, is more preferably between 150,000 and 2,000,000, and is further more preferably between 150,000 and 1,500,000. The content of the same is preferably between 5 and 40 percent by weight with respect to the sum of the resinous components. The molecular weight distribution Mw/Mn is to be at least 4, and is preferably between 5 and 80. Such high molecular weight vinyl based. resinous components are hard as well as brittle, and thus affect brittleness as well as blocking resistance. By subjecting said resinous components to stay within the aforementioned ranges, the brittleness as well as the blocking resistance is further improved.
When toner performance such as blocking resistance, low temperature fixability, and the like, are noted, the softening point of components in the low molecular region, which compose the matrix phases, is preferably between 80 and 150xc2x0 C., and is more preferably between 85 and 140xc2x0 C. Further, variance (weight average molecular weight/number average molecular weight) in the molecular weight distribution is preferably no more than 5, and is most preferably no more than 4.
Herein, the softening point was determined as follows. By employing an elevated type flow tester, one gram of a sample is extruded from the narrow hole of a die (1 mm diameterxc3x971 mm) under conditions of a load of 20 kg/cm2 and a rate of temperature increase of 6xc2x0 C./minute, and a flow curve is drawn which shows the relationship between the plunger descending distance and the temperature. Then the softening point was obtained as being the temperature when the descending distance of said plunger was one half of the full stroke. Further, the variance in the molecular weight distribution is the ratio of weight average molecular weight to number average molecular weight which is measured employing gel permeation chromatography.
The inventors of the present invention have discovered that the toner achieves the aforementioned objects of the present invention, which comprises resinous compositions which have a molecular weight distribution having two peaks and are comprised of matrix phases as well as domain phases dispersed in said matrix phases along with at least one type of fatty acid esters represented by general formulas (1-1) through (1-4) and a compound represented by general formula (2).
Namely, at least one type of fatty acid ester represented by general formals (1-1) through (1-4) as well as a carboxylic acid represented by the general formula (2) is incorporated into the toner of the present invention.
R1COOR2xe2x80x83xe2x80x83General Formula (1-1)
wherein at least one of R1 and R2 represents an aliphatic group having from 14 to 40 carbon atoms, preferably from 14 to 36 carbon atoms, and most preferably from 14 to 32 carbon atoms, and represents an alkyl group and an alkenyl group as the aliphatic group. Said alkyl groups include, for example, a myristyl group, an acetyl group, an octadecyl group, and the like. Further, said groups may be an alkyl group having a branch. Still further, the alkyl group may be substituted with another xe2x80x94OCOxe2x80x94R1. Listed as alkenyl groups are an octadecenyl group and the like.
When either R1 or R2 represents an aliphatic group having from 14 to 40 carbon atoms, the other group may represent an alkyl group having no more than 14 carbon atoms, such as a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group, an octyl group, a decyl group, a dodecyl group, and the like, a cycloalkyl group such as a cyclohexyl group, a cyclopentyl group, an alkenyl group such as a vinyl group, an allyl group, a butenyl group, a hexenyl group and the like, or an aralkyl group such as a benzyl group, a furfuryl group. Further, these alkyl groups, as well as aralkyl groups, may have a branch such as, for example, an isopropyl group, a tert-butyl group, a sec-butyl group, an ethylhexyl group, and the like. Still further, they may have a branch as exemplified by an isobutenyl group. The sum of the number of carbon atoms of R1 and R2 is at least 15, and is preferably between 15 and 60.
[R1COOxe2x80x94(CH2)n]axe2x80x94Cxe2x80x94[(CH2)mxe2x80x94OCOR2]bxe2x80x83xe2x80x83General Formula (1-2)
wherein a and b each represents an integer of 0 to 4; a+b is 4; R1 and R2 each represents an organic group having from 1 to 40 carbon atoms, and preferably from 2 to 36 carbon atoms; the difference in the number of carbon atoms between R1 and R2 is at least 3 and is most preferably 4 to 30; m and n each represents an integer of 0 to 25, and preferably an integer of 0 to 10; and m and n do not represent 0 at the same time.
[R1COOxe2x80x94(CH2)n]axe2x80x94Cxe2x80x94[(CH2)mxe2x80x94OH]bxe2x80x83xe2x80x83General Formula (1-3)
wherein xe2x80x9caxe2x80x9d represents an integer of 0 to 4; xe2x80x9cbxe2x80x9d represents an integer of 1 to 4; a+b is 4; R1 represents an organic group having from 1 to 40 carbon atoms, and preferably from 2 to 36 carbon atoms; m and n each represents an integer of 0 to 25, and preferably of 0 to 10; and m and n are not 0 at the same time.
[R1COOxe2x80x94(CH2)n]axe2x80x94C(R3)kxe2x80x94[(CH2)mxe2x80x94OCOR2]bxe2x80x83xe2x80x83General Formula (1-4)
(xe2x80x9caxe2x80x9d and xe2x80x9cbxe2x80x9d each represents an integer of 0 to 3; a+b is 1 to 3; R1 and R2 each represents an organic group having from 1 to 40 carbon atoms in integer, and preferably from 2 to 36 carbon atoms; the difference in the number of carbon atoms between R1 and R2 is at least 3, preferably 4 to 30; R3 represents a hydrogen atom or an organic group having carbon atoms of at least 1 (however, when a+b is 2, either one of R3 represents an organic group having at least 1 carbon atom); k represents an integer of 1 to 3; m and n each represents an integer of 0 to 25; and m and n are not 0 at the same time.)
It is possible to produce these esters employing well-known methods. Namely, methods are employed in which synthesis is carried out employing carboxylic acids and derivatives thereof, or ester incorporation reaction represented by the Michael addition reaction, and the like. Particularly preferred are methods in which dehydration condensation reaction of carboxylic compounds with alcoholic compounds is utilized or reaction of alcoholic compounds with acid halide compounds is utilized.
Specific examples of esters represented by general formula (1-1) include stearyl stearate, behenyl stearate, octyl stearate, decyl stearate, octyl melissinate, and the like. Further, as specific examples of esters represented by general formulas (1-2) through (1-4), 
are listed.
Further, listed as carboxylic acids employed in the present invention are those represented by general formula (2).
R4xe2x80x94COOHxe2x80x83xe2x80x83General Formula (2)
In carboxylic acids represented by general formula (2), R4 represents a saturated or unsaturated aliphatic group having at least 13 carbon atoms. Examples of carboxylic acids having a saturated aliphatic group include myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanic acid, arachidic acid, behenic acid, heptaconic acid, montanic acid, melistic acid, lacelic acid, and the like, while examples of carboxylic acids having unsaturated aliphatic group include linoleic acid, linoleic acid, arachidonic acid, and the like. Listed as preferred acids are behenic acid and stearic acid.
Of said compounds, the content of esters is generally in the range of 0.05 to 20 percent by weight with respect to the resinous components, and is preferably in the range of 0.15 to 10 percent by weight.
Further, the content of carboxylic acids is generally in the range of 0.001 to 5 percent by weight with respect to the resinous components, and is preferably in the range of 0.005 to 2 percent by weight.
Further, the content of preferred ester components is preferably between 80.0 and 99.0 percent by weight while the content of carboxylic acids is preferably between 0.1 and 20 percent by weight.
Compounds represented by the aforementioned general formula (3) are incorporated into the resinous composition of the present invention. Further, these compounds are well dispersed along with resinous components, and exhibit thermal stability at temperatures at which melt-kneading can be carried out efficiently. In addition, these are colorless substances and also are capable of imparting a negative charge to the toner. Thus it is possible to provide the toner with excellent chargeability.
In the formula, R4 through R7 each represents a hydrogen atom, and a univalent substituent, and preferably represents a halogen atom, an alkyl group, an alkoxy group, an aryl group, an aralkyl group, a hydroxyl group, a carboxyl group, a nitro group, a cyano group, and the like.
The halogen atom represents an atom such as fluorine, chlorine, bromine, and the like, and alkyl groups such as an alkyl group, an alkoxy group, and the like are the same as those represented by R1 and R2 in the aforementioned fatty acid esters as well as fatty acids. The aryl groups include unsubstituted aryl groups such as a phenyl group as well as a naphthyl group, and further these substituents may be further substituted with another substituents such as a tolyl group, a methoxyphenyl group, a chlorophenyl group, a hydroxyphenyl group, a carboxyphenyl group, a cyanophenyl group, and the like. The aralkyl groups include groups such as a benzyl group, a phenetyl group, and the like, and these groups may be further substituted with substituents such as those described above. Further, each phenyl ring may be substituted with a plurality of these groups, and for instance, a dichlorophenyl, a trichlorophenyl group, and the like, may also be employed. Still further, these substituents may form a condensed ring such as a naphthyl ring and the like, along with a phenyl ring.
M represents a trivalent metal, and said metal may be selected from Cr, Al, Fe, Co, Ti, B, and the like. Employed as univalent or divalent cations represented by X, which are employed to neutralize the charge, can be various types of inorganic cations, as well as organic cations. Listed as inorganic cations are hydrogen ions and metal ions. Listed as univalent, as well as divalent metal ions, are Li+, Na+, K+, Mg2+, Ca2+, Zn2+, and the like. Further, listed as organic cations are an ammonium ion, an iminium ion, a phosphonium ion, and the like. When X is a divalent cation, it is regarded as one half equivalent to neutralize charge.
Of the aforementioned organic cations, those which are preferred are represented by general formulas (3-1), (3-2), and (3-3) or (3-4) described below. 
wherein R8, R9, R10, R11, R12, R13, R141 R15, R16, R17, and R18 each represents a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group, while Z1 and Z2 each represents a nonmetallic atomic group which bonds to a nitrogen atom in each formula to form a 5-membered or 6-membered ring. Herein, listed as an alkyl group may be, for example, a methyl group, an ethyl group, an iso-amyl group, a n-dodecyl group, a n-octadecyl group, a cyclohexyl group, and the like. Listed as an aryl group may be, for example, a phenyl group, an xcex1-naphthyl group, and the like.
These alkyl groups or aryl groups may be substituted with various types of substituents such as an alkyl group, an. aralkyl group, a halogen, an alkoxy group, a hydroxyl group, a cyano group, an aryl group, and the like. Further, Z1 and Z2 each represents a nonmetallic atomic group necessary for forming various types of heterocyclic rings such as, for example, a pyridine ring, an isoquinoline ring, a pyrrole ring, an imidazole ring, a piperazine ring, a pyrrolidine ring, and the like.
Specific examples of compounds represented by general formula (3) are shown blow. 
The compounds represented by general formula (3), which are employed as the charge control agents of the present invention, are obtained employing a method described in, for example, Japanese Patent Publication No. 7-13765.
The added amount of these compounds represented by general formula (3), which are incorporated into toner components, is generally between 0.1 and 10 weight parts with respect to 100 weight parts of the resin, and is preferably between 0.5 and 5 weight parts.
Further, crystalline compounds having a low melting point are preferably incorporated in the present invention.
Said crystalline compounds, having a low melting point employed in the present invention, are those having a polar group at their terminals. Preferred polar groups include, for example, xe2x80x94OH, xe2x80x94Nxe2x95x90, xe2x80x94Sxe2x80x94, xe2x80x94COOH, xe2x80x94CHO, xe2x80x94SO3, xe2x80x94CN, xe2x80x94NO2, and a halogen atom. Of said crystalline substances, those having xe2x80x94OH (a hydroxyl group) are preferred due to the ease of controlling the charge amount of toner as well as their ease of synthesis.
Said crystalline compounds having a low melting point preferably have a melting point of 50 to 130xc2x0 C. When the melting point is below 50xc2x0 C., storage stability is degraded, while when the melting point is at least 130xc2x0 C., fixability at lower temperatures is occasionally degraded.
Listed as said crystalline compounds having a low melting point are low molecular weight crystalline compounds as well as the crystalline polymers described below. Specific examples of said low molecular weight crystalline compounds include, for example, higher alcohols such as 1-hexadecanol, 1-heptadecanol, stearyl alcohol, 1-nonadecanol, 1-eicosanol, 1-docosanol, 1-tricosanol, 1-tetracosanol, ceryl alcohol, and the like; higher fatty acids such as palmitic acid, heptadecanic acid, stearic acid, nonadecanic acid, eicosanic acid, behenic acid, triconsanic acid, lignoceric acid, and the like, as well as esters thereof; and further fatty acid amides such as linoleic acid amide, ricinoleic acid amide, erucic acid amide, oleinic acid amide, eicosanic acid amide, ercicic acid amide, palmitoleic acid amide, and the like.
Further, specific examples of said crystalline polymers include, for example, polyesters obtained by polycondensing polyols such as ethylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, hexamethylene glycol, tetramethylene glycol, and the like with polybasic acids such as fumaric acid, maleic acid, itaconic acid, terephthalic acid, succinic acid, adipic acid, sebacic acid, and the like; polyethers such as polyethylene glycol, polypropylene glycol, and the like; polymers having as the primary polymerization devices long chain alkyl esters such as behenyl acrylate, behenyl methacrylate, behenyl itaconate, stearyl itaconate, and the like.
Of these, crystalline polyesters are particularly useful. Representative examples include crystalline polyester resins (HP-320 of Nihon Gosei Kagaku Co., Ltd.) (having a Tsp of 80xc2x0 C.).
The content of said crystalline compounds, having a low melting point, is between 1 and 30 percent by weight with respect to the resinous composition. When the content of said crystalline compounds, having a low melting point, is below one percent by weight, the entire crystallinity of the resinous composition decreases to degrade the fixability at lower temperatures, while when the content of the same exceeds 30 percent by weight, the plasticity of the resinous composition progresses to degrade storage stability.
In the present invention, in order to improve the offset properties of toner during thermal fixing, it is preferable that further employed as releasing agents are polyolefin waxes of olefins such as low molecular weight polypropylene, low molecular weight polyethylene, ethylene-propylene copolymers, and the like.
The softening point (determined in accordance with the ring and ball method of JIS K 2531) of polyolefin wax releasing agents is preferably in the range of 100 to 160xc2x0 C. Of these, particularly preferred are low molecular weight olefin waxes having a number average molecular weight of 2,000 to 8,000, that is, low molecular weight polypropylene and low molecular weight polyethylene. Listed as any of these examples are polypropylenes (Viscol 660P).
The blending ratio for addition of these releasing agents is preferably between 1 and 10 weight parts per 100 weight parts of the binder resin.
If desired, other releasing agents may be incorporated into the electrophotographic toner of the present invention. Listed as such are ikurocrystalline wax, carnauba wax, sazol wax, paraffin wax and the like, which have been conventionally employed. When added, they are blended within the aforementioned range.
In the resinous compositions for toners which are comprised of matrix phases as well as domain phases dispersed into said matrix phases, compatibilizers, other than the aforementioned additives, are preferably incorporated.
Employed as the compatibilizers. used in the present invention are block copolymers, graft copolymers, star-shaped polymers, and the like, which comprise the same components as the matrix phase and the domain phase, or components which are compatible with both phases or one of the phases. Of these, preferably employed are block polymers or graft copolymers.
The reasons to employ the block copolymers, graft copolymers, star-shaped polymers, and the like, are as follows. These decrease free energy localized in the interface, and stabilize the less shaped domains. Thus these exhibit effects to markedly enhance the interaction of each interface.
For instance, in the case of a diblock copolymer comprised of two components similar to the components of the domain phase as well as the matrix phase, each of homopolymer components is compatible with each of the matrix phase and the domain phase and is capable of generating strong interaction between both phases. Consequently, the domain phase as well as the matrix phase is provided with the interaction, and the viscosity of all the resins is increased. As a result, the offset resistance is markedly improved.
It is preferable that without breaking each independent structure of the domain phase and the matrix phase, compatibilizers are localized in the interface, and generate strong interaction between both phases. Resin compositions, which are readily compatible with each phase, are comprised of at least one of said resin components which are capable of forming the matrix phase as well as the domain phase. Resin components are selected from, for example, vinyl based resins, xylene resins, epoxy resins, coumarone-indene resins, SBS resin, and the like. Specifically and suitably employed are vinyl based resins. Of these, styrene based copolymers, acrylic or methacrylic ester based copolymers, and styrene-acrylic or methacrylic copolymers are more suitable.
Employed as one type of compatibilizers are polymers having in the molecular chain a functional group capable of forming a hydrogen bond or an ionic bond. Such compatibilizers having such functional groups are dispersed in resinous compositions (the domain phase as well as the matrix phase) for said toner, and allow molecules to perform strong psuedo-crosslinking so that the interaction between the domain phase and the matrix phase is strengthened. Consequently, the domain phase and the matrix phase are capable of carrying out cooperative movement and thus offset resistance is improved.
The compatibility of compatibilizers to each phase is preferably to such a degree that without destroying each independent structure of the domain phase as well as the matrix phase, an interaction between both phases is generated. Herein, preferably incorporated as the aforementioned functional groups in the high molecular polymers are a hydroxyl group, and compounds such as ketones, esters, ethers, nitrites, halogens, sulfides, thiols, organic phosphorus compounds, nitro compounds, and the like.
Selected as resinous compositions, which are readily compatible with each phase, are resins which are capable of carrying out interaction with the matrix phase as well as with the domain phase, and are specifically selected from vinyl based resins, epoxy resins, and the like. Suitably employed are particularly styrene based copolymers, sulfonated polystyrene, polyvinyl butyral, partially saponified vinyl acetates, polyethylene glycol, polyvinyl bromide, polyurethane, and the like.
Employed as the other types of compatibilizers used in the present invention are polymers having a solubility parameter (xcex4) between those in the matrix phase and in the domain phase. The xcex4 value as described herein is calculated from the evaporation energy and volume per mole of a segment when a polymer chain is cut into segments having the approximately same volume as that of a solvent molecule, and is the value generally showing the chemical affinity of the polymer.
Reasons to employ such polymers are as follows: these polymers are localized at the interface and decrease free energy. Further, by decreasing domain sizes and stabilizing domains, the compatibilizers exhibit effects to markedly enhance the interaction at the interface.
Further, such polymers are partially compatible with the matrix phase as well as the domain phase and are capable of generating strong interaction between both phases. As a result, it is possible to minimize slippage of the domain phase and the matrix phase. Due to that, adhesive force between the domain phase and the matrix phase is enhanced, and the offset resistance is markedly improved.
Preferred compatibility of compatibilizers with each phase is in such a degree that without destroying each independent structure of the domain phase as well as the matrix phase, said compatibilizers are localized in the interface and generate strong interaction between both phases. The resinous compositions, which are readily compatible with each phase, are selected from, for example, vinyl based resins, xylene resins, epoxy resins, coumarone-indene resins, SBS resin, dines, and the like. Employed as particularly suitable resins are vinyl based resins. Of these, more suitable are styrene based copolymers, acrylic or methacrylic acid ester based copolymers, and styrene-acrylic or methacrylic acid copolymers. Specifically, styrene-n-butyl acrylate-methyl methacrylate copolymer (St-BA-MMA copolymer having a weight average molecular weight Wn of 500,000), which is employed in the production example of Example 1, is useful.
Employed as further different compatibilizers used in the present invention are polymers having a solubility parameter (xcex4), which is at most two than that of the matrix phase. Further, employed as the compatibilizers are those which preferably have a melt viscosity greater than the matrix phase.
The aforementioned polymers are employed to increase the melt viscosity of the matrix phase to decrease the domain sizes dispersed in the matrix phases and to control mechanical shearing force to effectively work on the interface of both phases.
Namely it is possible to markedly enhance the interaction between the domain phase and matrix phase by increasing the viscoelaciticity of the matrix phase as well as enhancing the dispersibility of the domain phase while allowing the matrix phase to be compatible with high molecular weight compounds having a high melt viscosity, which are perfectly compatible only with the matrix phase and are capable of forming an individual structure.
Such polymers are completely dissolved in the matrix phase and result in strong interaction between both phases by enhancing the viscoelaciticity of the matrix phase. Accordingly, it is possible to minimize slippage between the domain phase and the matrix phase. As a result, the offset resistance is highly improved.
Employed as resins which are readily compatible with each phase, as noted above, are vinyl based resins, diene based resins, and the like. Of these, employed may be butadiene, isoprene, isobutylene, polyethylene, and the like.
Employed as still other compatibilizers are polymers having a solubility parameter value (xcex4 value) which is larger at most two than that of the domain phase. Further the melt viscosity of compatibilizers employed herein is greater than that of the domain resins.
Such polymers are employed to decrease the viscosity of the domain phase during melting by decreasing sizes of the domain dispersed in the matrix phase so that mechanical shearing force is effectively applied into both phases.
Namely it is possible to markedly enhance the interaction between the domain phase and the matrix phase by decreasing the viscoelaciticity of the domain phase as well as enhancing the dispersibility to the matrix phase while allowing the high molecular weight compounds having a low melt viscosity, which are compatible only with the domain phase and are capable of forming an individual structure, to be compatible with the domain phase.
The aforementioned polymers are completely dissolved in the domain phase and are capable of resulting in strong interaction between both phases by decreasing the viscoelaciticity of resins in the domain phase, and by enhancing the dispersibility of the domain phase. Accordingly, it is possible to minimize slippage between the domain phase and the matrix phase. As a result, it is possible to highly improve the offset resistance.
Employed as resins, which are readily compatible with the domain phase, are, for example, vinyl based resins. Of these, employed are polymethyl acrylate, polyethyl acrylate, polyvinyl acetate, polyvinyl butyral, partially saponified polyvinyl acetates, and the like.
The added amount of these compatibilizers is preferably in the range of 0.01 to 40 percent by weight with respect to the total resinous components (the sum of resinous components constituting the domain phase as well as the matrix phase). When the content of said compatibilizers is less than the lower limit, the offset resistance of resins is degraded, while when the content is greater than the higher limit, domain/matrix structure exhibits perfect compatibility and it is impossible to obtain excellent fixability.
As described above, the resinous compositions for the toner of the present invention are produced as follows. For example, a specified amount of compatibilizers are blended with high molecular weight vinyl based resinous components, and the resulting blend is melt kneaded, employing a roll mill, a kneader, an extruder, or the like. Thus the resinous components, which constitute the domain phase, are prepared. Then said domain phase constituting resinous components are blended in a specified ratio with high molecular weight vinyl based resinous components which constitute the matrix phase, and the resulting blend is further melt kneaded employing a roll mill, a kneader, an extruder, or the like.
Further, the resinous compositions for the toner of the present invention are also produced as follows. A specified amount of compatibilizers are blended with the aforementioned low molecular weight vinyl based resinous components, and the resulting blend is melt kneaded employing a roll mill, a kneader, an extruder, or the like. Thus the resinous components, which constitute the matrix phase, are prepared. Then said matrix phase constituting resinous components are blended in a specified ratio with high molecular weight vinyl based resinous components which constitute the matrix phase, and the resulting blend is further melt kneaded employing a roll mill, a kneader, an extruder, or the like.
Further, as described above, domain phase constituting resinous components, comprising the compatibilizers, and matrix phase constituting resinous components, comprising the compatibilizers are individually prepared, and these are melt kneaded employing a roll mill, a kneader, an extruder, or the like. Thus it is possible to produce the resinous compositions for toner of the present invention.
Further, in some cases, said low molecular weight vinyl based resinous components and high molecular weight resinous vinyl based components are blended together, and the resulting blend is melt kneaded employing a roll mill, a kneader, an extruder, or the like. Thus it is possible to produce the resinous compositions for toners of the present invention.
Still further, in some cases, it is possible to produce the resinous compositions for toners of the present invention by blending, in suitable organic solvents, said low molecular weight vinyl based resinous components as well as high molecular weight resinous vinyl based components with compatibilizers and fixing aids.
Still further, it is possible to produce the resinous compositions for toners of the present invention by blending compatibilizers with either or both resinous components during the polymerization process of said low molecular weight vinyl based resinous components as well as high molecular weight resinous vinyl based components. In this case, when monomers, which constitute resinous components, are specifically polymerized (or copolymerized) in the presence of monomers which constitute the other resinous components, it is possible to more economically produce the resinous compositions for toners. In addition, it is preferred because compatibilizers, being fine inorganic particles described below, and the like, can be readily incorporated.
In any of the methods described above, it is possible to control the dispersion state of both resinous components of the domain phase and the matrix phase of resinous compositions for toners in a state in which compatibilizers and other additives are selectively incorporated into the domain and/or matrix phase by suitably controlling the compositions of components of low molecular weight vinyl based polymers and high molecular weight vinyl based polymers, weight average molecular weights, glass transition temperatures, types of compatibilizers, types of other additives, solution blending conditions, polymerizing (copolymerizing) conditions, and melt-kneading conditions.
When both resinous components described above are uniformly compatible with each other at the molecular level, they exhibit a compatible structure (a monophase structure) in a homogeneous system, and properties of both resinous components are averaged. As a result, it is impossible to obtain the fixing temperature, offset resistance, blocking resistance, and pulverizing properties, which are required for toners. Contrary to this, when both resinous components described above are non-uniformly compatible with each other at the molecular level, they preferably exhibit a microscopically phase-separated structure (a double-phase structure) in a heterogeneous system.
The resinous compositions for toners of the present invention comprise the micro-phase separation structure in a heterogeneous system, described as the latter case above, and are specifically comprised of the matrix phase (a continuous phase) as well as the domain phase (a discontinuous phase) which is dispersed in said matrix phase, and compatibilizers are incorporated into said domain phase and/or in the interface with the matrix phase. Herein, the most important point is that when there is no interaction or small interaction between the matrix phase and the domain phase, or when the domain size is very large, the domain phase behaves independently in the matrix phase and thus does not contribute to the improvement of offset resistance, which is the effect obtained by the domain phase. As noted above, since the domain phase and the matrix phase are independent of each other, the adhesion at their interface is weak. Due to that, in order to result in strong interaction at said interface, compatibilizers are effectively employed.
Further, such special micro-phase separation structures include those in which, specifically, the domain phase is granular, cylindrical, lamellar, and a mutually interpenetrating net. Such a micro-phase separation structure (a double-phase structure) can be confirmed by observing, for example, an ultra-microtome slice with the use of a scanning or transmission type electron microscope, or the like.
In the resinous compositions for toners of the present invention, it is specifically preferable that the domain phase has a particle-shaped structure and the size of the domain particles is approximately no more than 5 xcexcm. When resins comprised of domain particles having an excessively large size are employed to produce toners, the number of domain particles incorporated into toner particles fluctuate and critically affect various physical properties.
In the toner of the present invention, in addition to the aforementioned components, colorants are incorporated. Said colorants are not particularly limited, and various types of conventional colorants known in the art are employed. For example, listed are carbon black, Nigrosine dyes, Aniline Blue, Charcoyl Blue, Chrome Yellow, Ultramarine Blue, Du Pont Oil Red, Quinoline Yellow, Methylene Blue chloride, Phthalocyanine Blue, Malachite Green Oxalate, lamp black, Rose Bengal, or the like. The employed amount of colorants is generally in the range of 0.1 to 20 weight parts per 100 weight parts of the binder resin.
Further, employed as magnetic material particles, employed to obtain magnetic toners, are particles of ferrite, magnetite, or the like, having an average particle diameter of 0.1 to 2 xcexcm. The added amount of magnetic particles is generally in the range of 20 to 70 percent by weight with respect to colored particles in the state in which external additives such as fine composite particles described below are removed.
Further, in order to enhance the flowability of toners, in addition to hydrophobic silica particles, toners may be constituted by externally adding fine inorganic particles such as titanium dioxide, and fine composite particles prepared by adhering silica or the like to fine organic particles. Specifically preferred as such fine inorganic particles are those which have been subjected to hydrophobic treatment employing silane coupling agents, titanium coupling agents, and the like.
It is preferable that in the particle distribution of the toner produced as described above, volume standard 10 percent average particle diameter D10, volume standard 50 percent average particle diameter D50, and volume standard 90 percent average particle diameter D90, satisfy the formula described below. When these conditions are satisfied, it is possible to obtain high quality fixed images which exhibit sufficient fixing strength over a wide fixing temperature range, and further form neither offset nor image dust.
D10 greater than 0.5xc3x97D50
D90 less than 1.5xc3x97D50
The toner, which is produced employing the resinous composition of the present invention, exhibits sufficient fixing strength over a wide fixing temperature range, and further makes it possible to obtain high quality images which result in neither offset nor image dust. Further, it is possible to apply said toner to various types of fixing devices.
It is possible to advantageously apply the toner, which is prepared employing the resinous composition of the present invention, to a flash fixing device employing a flash lamp described in Japanese Patent Publication Open to Public Inspection No. 7-199715, U.S. Pat. No. 5,151,743, and others; a heated belt fixing device employing a heated film as described in Japanese Patent Publication Open to Public Inspection Nos. 8-6409 and 8-76515; and further, a heated roller fixing device as described in Japanese Patent Publication Open to Public Inspection No. 8-76515.